E.ON Next use Kraken IT plaform by Octopus Tech. So it gets monthly billing.
E.ON which it's own energy mix it sells domestic customers as E.ON Next is more renewable , it sells it dirty energy for cheap to Utility Warehouse to push through it's MLM model
Like many Energy companies, several Facebook groups have sprung up, where customer help each, but like many groups on FB beware of scammers or just that whose interests are not your own. While there can be good advice there can also be plenty of misinformation